Leaders from Georgia and Ukraine have withdrawn from an informal summit of former Soviet states.

A spokesman for Mikhail Saakashvili said Friday, the Georgian president canceled his trip to Moscow partly due to cabinet changes in Tblisi. Officials said he had hoped to hold talks with Russia on the situation in South Ossetia, but was unable to schedule a meeting.

Tension has been rising between Tblisi and Moscow over the region, where Georgian forces are engaged in an armed standoff with separatists. Earlier this week, Georgian lawmakers passed a resolution demanding Russian peacekeepers leave the region.

Ukrainian President Viktor Yushchenko has also pulled out of the summit, citing a political crisis in Kiev that could force him to dissolve parliament.